Mixing, kneading, and shredding blade



April 3, 1934 H. BQVOLLRATH MIXING, KNEADING, AND SHREDDING BLADE Filed NOV. 30, 1931 Patented Apr. 3, 1934 PATENT OFFICE,

MIXING, KNEADING, AND SHREDDING BLADE Harold B. Vollrath, Bronxville, N. Y., a'ssignor to Baker Perkins Company, Inc., Saginaw, Mich., a corporation of New York Application November 30, 1931, Serial No. 578,043

4 Claims.

'10 suitable meansforrotating the blades therein.

The blades are horizontally disposed and parallel to each other and their axles pass through the two end walls of the trough. The distance between the blade centers is just slightly greater than the sum of the radii of the two blades, so that the peripheral edge of each blade in rotation describes a cylinder, the two cylinders not intersecting. The bottsm of the trough shell, which in conjunction with the trough ends comprises the complete trough, is formed into two part-cylinders whose centers coincide with the blade I centers and whose radii are just slightly greater than the blade radii so that the blades may rotate therein without contact. The curvature of the lower part of the trough shell begins at or may begin somewhat above the center of the blade axes on both its front and back walls, but discontinues ata point somewhat below the blade centers as it follows the arc upward from the bottom between the two blades. At-this termination or juncture of the two co equal curved sections of the trough bottom is located a serrated saddle or suitable roughened surface across which pass with close clearance serrations, or teeth, out in the peripheral edges of theblades or cut into shoes or members which in turn are fastened to the faces of the blades.

The trough is usually a double-walled vessel providing a jacket space for the circulation of a suitable medium for maintaining and controlling the temperature of the'material to be treated in the machine.

The following example is cited as one of the several common uses of this type of mixing and shredding machine:

In the treatment ofalkali cellulose for conversion into viscose in the manufacture of rayon or any other commercial product made from viscose, the cellulose is first mercerized by steeping 50 in a caustic soda solution. Before removal from the steeping tank, the alkali cellulose is squeezed or pressed until there remains absorbed in it only a definite amount of caustic soda solution. Later, this alkali cellulose is destined to be brought into contact with carbon bisulphide, which reaction produces cellulose xanthate. But in order that there shall be a complete reaction between the carbon bisulphide and the fibrous alkali cellulose,

it is necessary that the compressed sheets of alkali cellulose coming from the steeping press shall first be greatly broken down and the matted fibres loosened up, fluiled, and exposed, or rendered into what is commonly termed alkali cellulose crumbs.

The mixing and shredding machine described above performs this function of shredding the compressed sheets and reducing them to crumbs of fluffy, loosened fibre. Simultaneously, it performs another desirable function by thoroughly mixing the entire charge of alkali cellulose and thereby insuring an equal distribution of caustic content throughout the batch, the caustic content of each of the many sheets of cellulose comprising a batch not having been in sured of equality when pressing in the steeping 5 press.

During the shredding process there is a criti cal temperature above which the alkali cellulose cannot be allowed to rise. The heat generated by the mechanical work of the machine is carried off by the cooling medium circulating through the jackets of the trough. This temperature limitation largely controls the time required to complete the shredding of the batch, for the heat generated is a result of the power applied to drive the blades, or heaters, and increases with the speed at which the blades are rotated. Furthermore, even could the heat generated by faster blade rotation be carried off satisfactorily, there is a speed above which the centrifugal force exerted by the rotating blades would throw the alkali cellulose upward and not drag it down across the serrated saddle, where the shredding is accomplished.

The present invention is a new type of blade, or beater, designed to accomplish more work in a unit of time than the former typeof blade without increasing the speed of rotation.

Figure 1 is a perspective view of a preferred form of a blade according to my invention.

Figure 2 is a perspective view of a mixer, kneader and shredder of typical design, in discharge position, showing an installation of my blade.

Figure l is a drawing of the blade, with serrated shoes attached. From the left hand axle 1 projects radially an equal distance in each direction an arm 2. From each outer end of the radial arm 2 there extend, toward the right, wings 3 and 4, to join the outer ends of the radial arm 5, from the center of which in turn extends the right hand axle 6. The right hand radial arm 5 is located with relation to the left hand radial arm 2, or vice versa, at an angle preferably of 90; that is, when one is in the horizontal plane, the other is in the vertical plane, although I do not limit myself to this specific angle. The object of this angle is to provide a twist to the blade wings, so that they describe a helix, the outer edges of the wings being kept on the same radius throughout their entire lengththe radius established by the length of the radial arms.

The object of the helical form of the blade Wings is twofold: it insures a mixing from end to end as well as from front to back of the trough of the material to be mixed and shredded; it minimizes the driving power required by having the blade gradually and progressively passing across the length of the serrated saddle, instead of all at once were the wing a straight line instead of a helix.

The advantages gained by the use of a pair of theseimproved blades in mixing and shredding machines, compared to the type of blades hitherto commonly used, are as follows:

First, each of the two blades mounted in the trough makes two passes across the entire length of the serrated saddle on one revolution, as compared to one pass made by the former blades. Thus, if the two blades are geared at the ratio, which I prefer, of 554, and rotating at speeds of 50 and 40 R. P. M., they will accomplish 180 passes across the saddle per minute, as compared to 90 passes per minute accomplished by the former blades running at the 'same'R. P. M. But the driving power required and the heat generatedwill be increased but slightly-in much lower proportion than the increase in work done per unit of time.

Second, by reason of their shape, these im proved blades are balanced and thereby minimize vibration, increasing the life of the machine.

Third, the load on the machine becomes less pulsating and more nearly constant, thus decreasing the wear on drive gears and bearings.

Fourth, by reason of their shape, greater torsional and deflecting stress can be withstood by these improved blades with the same weight of metal as the former blades.

What I claim and desire to secure by Letters Patent is:

1. In a machine of the class described, having a bowl with double arcuate bottoms, whose arcs approximately touch each other at the plane of their centers, a saddle formed by the upwardly extending arcs at the center of said bowl, projections on the face of said saddle, blades rotatably mounted in the bowl at the center of said arcs and adaptedto rotate toward each other at different speeds, said blades rotating in paths whose arcs are slightly less than the radii of said first mentioned arcs, each blade consisting of a pair of radially disposed arms located in diiferent planes, a pair of blade wings extending spirally from the ends of one arm to the ends of the other arm, and teeth with their apices in the plane of rotation on' the working face of said wings.

2. In a machine of the class described, having a bowl with double arcuate bottoms, whose arcs approximately touch each other at the plane of their centers, a saddle formed by the upwardly extending arcs at the center of said bowl, projections on the face of said saddle, blades rotatably mounted in the bowl at the center of said arcs and adapted to rotate toward each other at different speeds, said blades rotating in arcs of slightly less diameter than said first mentioned arcs, each blade consisting of a pair of radially disposed arms located in different planes, a pair of blade wings extending spirally from the ends of one arm to the ends of the other arm, a shoe on the face of said blade wings, and teeth with their apices in the plane of rotation on the edge of said shoe.

3. In a machine of the class described, having a bowl with double arcuate bottoms, a saddle formed at the center of said bowl by the upwardly extending arcs, which approximately touch each other at the plane of their centers, projections on the face of said saddle, blades rotatably mounted in the bowl at the center of said arcs and adapted to rotate toward each other, in arcs of slightly less radii than the first mentioned arcs, each blade consisting of a pair of radially disposed arms located in different planes, a pair of blade wings extending spirally from the ends of one arm to the ends of the other arm, and teeth with their apices in the plane of rotation on the working face of said wings.

4. In a machine of the class described, having a bowl with double arcuate bottoms, whose arcs approximately touch each other at the plane of their centers, a saddle formed at the center of said bowl by the upwardly extending arcs, projections on the face of said saddle, blades rotatably mounted in the bowl at the center of said arcs and adapted to rotate toward each other in arcs of slightly less radii than the first mentioned arcs, each blade consisting of a pair of radially disposed arms located in different planes, a pair of blade wings extending spirally from the ends of one arm to the ends of the other arm, a shoe on the face of said blade wings, and teeth with their apices in the plane of rotation on the edge of said shoe.

HAROLD B. VOLLRATH. 

